If a routine coliform bacteria sample is positive, how many additional samples must a water supplier take?

When a routine coliform bacteria sample from a water supply is found to be positive, it indicates a potential contamination issue that needs to be addressed promptly. The regulatory framework requires that, in response to a positive sample, a water supplier must take additional samples to confirm or rule out the presence of bacteria in the water system.

Taking additional samples is crucial because it helps determine whether the positive result was a one-time issue or indicative of a broader problem within the water system. The standard procedure stipulates that the supplier must collect a total of four repeat samples from both the immediate area of the original positive sample and other locations within the distribution system. This protocol helps ensure an accurate assessment of water quality and identifies any necessary actions to safeguard public health.

By collecting these four additional samples, the water supplier can effectively monitor the water quality and respond accordingly based on the results of the follow-up tests. If the follow-up tests reveal further contamination, more extensive measures may need to be implemented to address the issue.